1. Field of the Invention
The invention relates to an electromagnetic actuator and, more particularly, to an image pickup apparatus which is used in an electronic camera or a video camera.
2. Description of Related Art
Actuator for generating a driving force utilizing an electromagnetic inductive action is generally used as a mechanism for driving optical parts such as a lens, a mirror, a prism, which are used in an image pickup apparatus or the like or small parts such as electronic parts or the like.
Since the conventional electromagnetic actuator has a structure constituting one driving system based on a driving force formed by the whole actuator, the driving force becomes small and there is a tendency that a response speed in generation of the driving force in response to an input control signal is slow. In association with it, in many cases, the actuator's performance in stably positioning the driven part to a predetermined driving position remains at a poor level.
In the image pickup apparatus which is used in an electronic camera, hitherto, a charge transfer unit such as a CCD (charge coupled device) or the like and a photosensitive unit are provided, the photosensitive unit has a solid state image pickup device in which photosensitive pixels are arranged in the vertical and lateral directions at a predetermined pixel pitch. An image of an object is converted into an electric signal by the solid state image pickup device and is outputted, and the output signal is formed as an image signal.
In the image pickup apparatus, however, since a resolution when an image of an object is photographed is determined by the number of pixels of the solid state image pickup device, it is necessary to increase the number of pixels or to raise the degree of integration of the solid state image pickup device in order to perform a high resolution photographing. However, there are problems that when the number of pixels is increased, the cost of the solid state image pickup device increases even if the degree of integration of the solid state image pickup device is not raised, or the degree of integration is raised with the size of photo-sensing surface of the solid state pickup devices unchanged, a high working precision is required, so that the costs of the solid state image pickup device further rise.